We're dividing 784303 by 21 
The aim is to understand the frequency of 21 in 784303.

Step 1:
21 goes into 7 0 times with a remainder of 7.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
The remainder is 7 after subtracting 0 from 7.
Fetch the next digit (8) from the dividend, attach it to 7 and continue: 78 / 21

Let's proceed to step 2:
78 divided by 21 is 3 with a remainder of 15.
Record the quotient 3 as the next digit in the result. 
Result so far: 3.0
If we take 63 away from 78, we end up with 15.
Fetch the next digit (4) from the dividend, attach it to 15 and continue: 154 / 21

Advancing to step 3:
21 goes into 154 7 times with a remainder of 7.
The next digit of our result is 7. 
Result so far: 37.0
If we subtract 147 from 154, we get 7.
Bring next digit (3) of the dividend behind the 7 and repeat the process: 73 / 21

Going ahead to step 4:
When dividing 73 by 21, we get 3 with a remainder of 10.
Write down 3 as next digit of the result. 
Result so far: 373.0
The remainder is 10 after subtracting 63 from 73.
Bring next digit (0) of the dividend behind the 10 and repeat the process: 100 / 21

Going ahead to step 5:
21 goes into 100 4 times with a remainder of 16.
Use 4 as the next digit of our solution. 
Result so far: 3734.0
Subtracting 84 from 100 leaves us with 16.
Include the next digit (3) from the dividend after 16, then repeat: 163 / 21

Going ahead to step 6:
The number 21 fits into 163 7 times, leaving a remainder of 16.
Use 7 as the next digit of our solution. 
Result so far: 37347.0
Deduct 147 from 163 and we're left with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Going ahead to step 7:
When dividing 160 by 21, we get 7 with a remainder of 13.
Use 7 as the next digit of our solution. 
Result so far: 37347.7
Subtracting 147 from 160 leaves us with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Going ahead to step 8:
If we divide 130 by 21, we get 6 and a remainder of 4.
Put 6 as the next digit of the answer. 
Result so far: 37347.76
Subtract 126 from 130 to get 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Let's proceed to step 9:
When dividing 40 by 21, we get 1 with a remainder of 19.
The next digit of our result is 1. 
Result so far: 37347.761
If we take 21 away from 40, we end up with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Step 10:
21 goes into 190 9 times with a remainder of 1.
Use 9 as the next digit of our solution. 
Result so far: 37347.7619
If we subtract 189 from 190, we get 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Let's proceed to step 11:
21 can be fit into 10 0 times, resulting in a remainder of 10.
Record the quotient 0 as the next digit in the result. 
Result so far: 37347.7619
The remainder is 10 after subtracting 0 from 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Let's proceed to step 12:
When dividing 100 by 21, we get 4 with a remainder of 16.
The next digit of our result is 4. 
Result so far: 37347.761904
Subtract 84 from 100 to get 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

On to step 13:
The number 21 fits into 160 7 times, leaving a remainder of 13.
Use 7 as the next digit of our solution. 
Result so far: 37347.7619047
Deduct 147 from 160 and we're left with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Step 14:
If we divide 130 by 21, we get 6 and a remainder of 4.
The next digit of our result is 6. 
Result so far: 37347.76190476
Subtract 126 from 130 to get 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Our division results in 37347.76190476 with a remaining 4e-09.